A surprising plot twist has emerged in the auction of TV broadcasting giant Tribune Media, with billionaire Leon Black’s buyout firm making an unusual acquisition to get a leg up against its big bidding rivals, The Post has learned.

Black’s Apollo Global Management — which is jockeying to buy the owner of 42 local TV stations, including Chicago’s WGN and New York’s WPIX, in a deal that could be worth more than $5.5 billion — has meanwhile cut a contingent deal to acquire Northwest Broadcasting, a Michigan-based local-TV broadcaster, sources said.

Apollo is scooping up little-known Northwest, headed by Chief Executive Brian Brady, because it holds valuable contracts with cable giants that Apollo believes will enable it to charge cable providers higher fees if it becomes Tribune’s owner.

Specifically, Northwest has won lucrative deals through hard-knuckle negotiations on so-called retransmission fees from big cable providers, including Verizon and Charter Communications.

In the case of Charter, Northwest in June ended a four-month dispute that had blacked out 11 stations, including an NBC affiliate.

“They went dark with Verizon and Cable One just last year,” Charter complained in a statement during the height of the battle. “They [Northwest] are demanding to be paid significantly more than we pay any other broadcast station for the same network programming.”

Northwest, which operates 12 network stations in California, Idaho, Mississippi, New York, Oregon and Washington, got at least some of its demands met.

Now, Black’s Apollo — which is pitted in the auction against Texas-based broadcasting giant Nexstar, which owns 171 stations — is looking to parlay Northwest’s winnings into a bigger advantage by combining the company with Tribune.

It aims to do so because of industry regulations that allow station owners with multiple network affiliates to operate them under the same terms — that is, the best terms that any single station has negotiated on retransmission fees with a given cable provider, a source said.

“What Apollo is buying is great contracts,” the source said.

At least four bidders are believed to be in the hunt for Tribune, and final bids were due Wednesday. Others in the hunt include comedian Byron Allen and a partnership that includes Cerberus Capital, Hicks Equity Partners and ION Media.

There is some irony if Apollo wins the Tribune Media auction.

Apollo was as recently as July in talks to buy Nexstar from its chairman and CEO, Perry Sook. Sook has had a long-running ambition to buy Tribune Media and become the nation’s biggest owner of TV stations.

But Sook, who founded Nexstar in 1996, changed his mind when regulators stopped Sinclair from completing its buyout of Tribune Media, putting Tribune Media back in play.

Sook then reversed himself and pursued Tribune Media.

Apollo and Tribune declined to comment. Northwest did not return calls.